The Cassini spacecraft observes three of Saturn’s moons set against the darkened night side of the planet. Saturn is present on the left this image but is too dark to see. Rhea (1,528 kilometers, or 949 miles across) is closest to Cassini here and appears largest at the center of the image. Enceladus (504 kilometers, or 313 miles across) is to the right of Rhea. Dione (1,123 kilometers, or 698 miles across) is to the left of Rhea, partly obscured by Saturn. Image taken April 25, 2011. (Credit: NASA/JLP/Space Science Institute)

Many people have a special place in their heart for the sixth planet from the Sun. Its elegant beauty has captured our imaginations ever since Galileo first looked at it through a telescope in the 1600s. This intrigue, as well as our innate curiosity, has lead us to study Saturn and uncover its mysterious. Now, some new data from the Cassini spacecraft suggests that Saturn’s intricate ring system and its dazzling moons are likely more than four-billion years old, meaning that both formed around the same time.

 

 

This highly enhanced color view was assembled from clear, orange and ultraviolet frames obtained 17 August 1981 from a distance of 8.9 million km (5.5 million miles).

If true, this means that the Saturnian system is a goldmine for information about the formation of our solar system. Since the planet’s rings and moons formed out of the same planetary nebula as the rest of the solar system, these objects work as a time capsule…preserving information about our solar system’s early history. Gianrico Filacchione, one of the scientists involved with Cassini, states that, “Studying the Saturnian system helps us understand the chemical and physical evolution of our entire solar system. We know now that understanding this evolution requires not just studying a single moon or ring, but piecing together the relationships intertwining these bodies.”

 

 

This data was provided by Cassini’s Visual and Infrared Mapping Spectrometer – VIMS for short. In this case, the spectrometer device was used to map the distribution of water-ice in the Saturnian system. Analyzing the concentrations of water-ice provides us with insight to the evolution of the objects in orbit around the ringed planet. Much to the surprise of researchers, VIMS showed a large amount of water-ice, far too much to have been delivered my comet’s or other more modern processes.

 

 

In addition, researchers have noticed that the moons of Saturn usually get redder the farther away from Saturn they are. This reddish hue is likely caused by the oxidized iron (a fancy way of saying ‘rust’) or possibly polycyclic aromatic hydrocarbons (a fancy way of saying PAHs). The VIMS analysis found an anomaly in Prometheus’ coloring, for it is far redder than it should be considering the ‘zone’ in which it orbits (the moons in this region tend to be whiter). This indicates that the moon may have formed out of the ring system. Currently, scientists believe that the Saturnian ring system was created by satellites that had broken up. Scientists have often wondered if the same process could work in reverse, where part of the ring gives rise to a moon and, well, it appears that might be the case.

 

All of this provides some reasonable evidence that Saturn, its moons, and the ring system, all formed around the same time as one another back in the very early days of our solar system.


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